1. Field of Invention
The present invention relates in general to housings for enclosing computer systems and in particular to vented covers with acoustic attenuation for use with such housings. Still more particularly, the present invention relates to a computer system which includes a vented cover having cross-flow ventilation ducts with an acoustic noise reduction lining.
2. Background Art
Computer systems are using larger amounts of energy, and are generating more heat. Increased heat generation is driven by factors such as increases in processor performance and clock speed, and increases in the number of devices per integrated circuit. Electronic components, such as microprocessors and integrated circuits, must operate within certain specific temperature ranges to perform efficiently. Excessive heat degrades electronic component performance, reliability, life expectancy, and can even cause failure. Air moving devices (AMDs), such as fans and blowers, are widely used for controlling excessive heat. AMDs are often used in combination with heat sinks thermally connected to electronic components to be cooled. Typically, heat sinks are formed with fins to increase the surface area of the heat sink and thereby enhance heat dissipation as air moved by an AMD passes over the heat sink.
In many large server applications, the processors of a computer system along with their associated electronics (e.g., memory, disk drives, power supplies, etc.) are packaged in removable drawer configurations stacked within a rack or frame. In other cases, the processors of a computer system along with their associated electronics may be in fixed locations within the rack or frame. Typically, the components are cooled by air moving in parallel air flow paths, usually front-to-back, impelled by one or more AMDs.
With the advent of the increased heat generated by computer systems, increased ventilation is required to move cooling air through the computer system. A failure to provide adequate ventilation through a computer system may increase the probability of computer failure due to overheating and may result in damage to the electronic components. Due to the great expense of these electronic components and the concomitant loss of processing time associated with such failures, it is desirable that adequate ventilation be maintained for computer systems. Increased air flow rates are needed to provide adequate ventilation. However, the acoustic noise associated with the increased air flow rates required to provide adequate ventilation, as well as acoustic noise generated by the various components within the computer system, represents a problem that must be overcome. There are limits on the acoustic output of computer systems (e.g., servers and storage products) set by vendors, governments, standards setting bodies, and the like.
In order to reduce acoustic noise, it is known to utilize an acoustic noise reduction lining in vented covers of computer systems. An example of such an arrangement is found in U.S. Pat. No. 5,526,228, issued Jun. 11, 1996 to Dickson et al., entitled “COMPUTER SYSTEM UNIT WITH ACOUSTIC DAMPENING COOLING FAN SHROUD PANEL”, which is assigned to the assignee of the present application. As shown in FIG. 1, a cooling fan shroud panel 101 includes an acoustic noise reduction lining comprising a side acoustic foam panel 102 and a top acoustic foam panel 104. The acoustic dampening cooling fan shroud panel 101 is mounted to an intermediate rear panel 106 of a computer system unit 100. Two cooling fans 108 are mounted within fan mounting apertures of the intermediate rear panel 106. The cooling fans 108 draw air through computer system unit 100 from an intake ventilation grill (not shown) of a front panel 110 in the direction indicated by the arrows designated with reference numeral 111. Mounted within computer system unit 100 are a power supply 112 and an electronic component package 114, which are cooled by the air drawn through computer system unit 100. Air is directed out an exiting ventilation aperture 116 of cooling fan shroud panel 101 in the direction indicated by the arrow designated with reference numeral 117. The exiting ventilation aperture 116 is displaced from the mounting position of the cooling fans 108 such that acoustic noise resultant from the cooling fan operation is diminished. Even though acoustic dampening cooling fan shroud 101 is effective in diminishing acoustic noise, it exhibits a number of disadvantages. First, the relatively substantial depth of acoustic dampening cooling fan shroud panel 101 significantly increases the footprint of computer system unit 100. Second, the small area of exiting ventilation aperture 116 relative to intermediate rear panel 106 reduces the cooling efficiency.
FIGS. 2 and 3 show other examples of the utilization of acoustic noise reduction lining in vented covers found in the IBM eServer zSeries 900 server. As shown in FIG. 2 (Top View), an inlet cover 210 includes an acoustic noise reduction lining comprising two outer acoustic foam panels 212 and central acoustic foam block 214. An inlet ventilation aperture 216 is defined between outer acoustic foam panels 212. Similarly, an exhaust cover 220 includes an acoustic noise reduction lining comprising two outer acoustic foam panels 222 and central acoustic foam block 224. An exhaust ventilation aperture 226 is defined between outer acoustic foam panels 222. The inlet cover 210 and the exhaust cover 220 are mounted to a computer system frame or rack 200 using hinges (not shown) so that removable drawers (not shown) stacked within computer system frame 200 may be accessed when inlet cover 210 and/or exhaust cover 220 is/are swung open via the hinges. AMDs (not shown) draw air through computer system frame 200 from inlet ventilation aperture 216 and exhaust the air through exhaust ventilation aperture 226. The air moves in the direction indicated by arrows designated by reference numeral 230. The removable drawers, which contain processors and their associated electronics, are cooled by the air drawn through computer system frame 200, as are electronic components fixed within computer system frame 200. Acoustic noise resultant from the AMD operation is effectively diminished by inlet cover 210 and exhaust cover 220 which have three main attributes: a large amount of acoustic absorbing material; an air/noise path that curves or angles to force sound to impact the acoustic lining; and minimum sharp bends in the air path to minimize airflow resistance. Even though inlet cover 210 and exhaust cover 220 are effective in diminishing acoustic noise, they exhibit a number of disadvantages. First, the relatively substantial depth of inlet cover 210 and exhaust cover 220 significantly increase the footprint of computer system frame 200. Second, the central acoustic foam block 224 in the exhaust cover 220 reduces cooling efficiency because it acts as a roadblock to exiting air. Third, inlet cover 210 and exhaust cover 220 cannot be made much more efficient without increasing airflow resistance, or increasing the cover depth (i.e., there are practical limits on how deep inlet cover 210 and exhaust cover 220 can be while still allowing the hinges to open).
FIG. 3 shows a modification of the configuration of inlet and outlet covers shown in FIG. 2 to reduce increase in the footprint of the computer system frame. As shown in FIG. 3, an inlet cover 310 includes an acoustic noise reduction lining comprising two angled outer acoustic foam panels 312 and central acoustic foam panel 314. An inlet ventilation aperture 316 is defined between angled outer acoustic foam panels 312. Similarly, an exhaust cover 320 includes an acoustic noise reduction lining comprising two angled outer acoustic foam panels 322 and central acoustic foam panel 324. An exhaust ventilation aperture 326 is defined between angled outer acoustic foam panels 322. The inlet cover 310 and the exhaust cover 320 are mounted to a computer system frame or rack 300 using hinges (not shown) so that removable drawers (not shown) stacked within computer system frame 300 may be accessed when inlet cover 310 and/or exhaust cover 320 is/are swung open via the hinges. AMDs (not shown) draw air through computer system frame 300 from inlet ventilation aperture 316 and exhaust the air through exhaust ventilation aperture 326. The air moves in the direction indicated by arrows designated by reference numeral 330. The removable drawers, which contain processors and their associated electronics, are cooled by the air drawn through computer system frame 300, as are electronic components fixed within computer system frame 300. As with the configuration shown in FIG. 2, acoustic noise resultant from the AMD operation is effectively diminished by inlet cover 310 and exhaust cover 320, but with a reduced footprint relative to the configuration shown in FIG. 2. Even though inlet cover 310 and exhaust cover 320 are effective in diminishing acoustic noise with a reduced footprint, these covers exhibit all of the other of disadvantages of the configuration shown in FIG. 2.
It should therefore be apparent that a need exists for a computer system enclosure which can both adequately ventilate a computer system housed therein and reduce the amount of acoustic noise, while addressing the disadvantages of the prior art.